Composite soldered heat exchanger



' 2,313,315 BLAIR March 9, 1943.

EMILIEN BLALS. COMMONLY KNOWN ASEMILE COMPOSITE SbLDERED HEAT EXCHANGER #920 5040:? SECr/OM' s 5M lw T l M RLNMM m3 mB B m c N w %R NNH o a vzom n u 5% IM A m m m w w S March 9, 1943.

EMILIEN BLAIS, COMMONLY KNOWN AS EMILE BLAIR COMPOSITE SOLDERED HEAT vEXCHANGER Filed May 5, 1941 2 Sheets-Sheet' 2 OFT Z9 Z5 Z8 Z9 25 29 6 SOFT INVENTOR:

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Patented Mar. 9, 1943 UNITED STATES" PATENT OFFICE COMPOSITE II EAT EXCHANGE-R Emilien Blais, commonly known as Emile Blair, New Haven, Conn., assignor to Western Gartridge Company, New Haven, Conn., a corporation of Delaware Application May 3, 1941, Serial No. 391,698

3 Claims. 257-128) to permit a fluid to flow around the tubestransversely of their lengths in heat exchange-relation with another fluid passing through the tubes.

Heat exchangers of the cartridge type have long been in successful commercial use as, for lexample, in radiators of automobiles. The ordinary commercial solder, sometimes called commonsolder, lead-tin solder or soft solder, used for bonding the enlarged tube ends together has suflicient strength for ordinary use. The usual manner of making these radiators is to assemble the tubes together in suitable frame and dip theends of the assembled tubes bodily into a bath of heat exchanger. Because of the high melting point of'silver solder it has been impractical to immerse the assembled tubes into a molten bath of the solder, but it has been necessary to apply the hard solder by hand, using a high temperature blow torch, as, for example, an acetylene torch, and applying the, solder by-melting a thin wire Or rod of the solder with suitable flux and separately bonding each tube to its adjacent tubes. Even here great care has to be taken to prevent damaging the tubes, heat absorbing bushings being provided within the enlarged tube endsto protect the tube walls from the intense heat. According to the present invention I provide a novel method of manufacture and an entirely new heat exchanger construction, overcoming, to

a great extent, the disadvantages due to the hard ,solder, while retaining all of its advantages. I have found that suflicient mechanical strength can be obtained by silver soldering only the marginal rows of tubes after which the-entire solder maintained at sufilciently' high tempera- 5 ture to keep the bath molten. This temperature will run for example, 725 F., depending upon the ,particular composition of the solder but well below any temperature which might burn or anneal the copper tubes. For certain work, particularly in airplanes, -where the radiator or heat exchanger is subject to severe vibration and where it is not permitted to make the parts heavier to obtain increased strength, the ordinary soft solder cartridge type radiators have not given satisfactory service. The soft solder has so little mechanicalstrength that cracks develop, causing leaks and the heat exchanger is shortly rendered unfit for service. V

In order to strengthen cartridge type heat exchangers I have proposed, in application Serial No. 211,979, filed June 6, 1938, to use a solder is found in the so-called silver solders which are radiator maybe dipped in the old fashioned soft solder, which not only bonds the interior. tubes but also adds additional bonding material to'the marginal tubes. This construction not only eliminates the tedious hand soldering'of the greater part of the tubes, but provides a hard soldered peripheral or marginal sleeve or cylinder classified as hard solders. Such a heat exchanger,

. of substantial thickness having, great mechanical strength against the various stresses-to which I light weight. airplane radiators are subjected.

particularly pointed out in the claims appended hereto, the invention itself, as. to its objects and advantages, and the manner in which'it may be carried out, maybe better understood by referring to the following description taken. in

connection with the accompanying v drawings forming a part thereof, in which I Fig. 1 illustrates somewhat diagrammatically one form of heat exchanger according-to the invention.

Fig. 2 illustrates frames for assembling the marginal hard soldered rows of tubes.

Fig. Sis an enlarged section taken through line 33 of Fig. 2.

Fig. 4 'is an enlarged fragmentary section taken through the completed heat exchanger.

Fig. 5 is, a fragmentary enlarged-end view, il-

" lustrating the appearance: of the completed heat exchanger; and v 1 maining tubes of the core.

is shown for purposes of illustration but it will be understood that the present invention is applicable to many other difierent types of heat exchangers.

The heat exchanger comprises in general a core soldering operations hereinafter set forth. The

turn buckles 26 will be turned to cause the tubes possible, to dipthe assembled tube ends in a bath I0 made up of a plurality .of rows of heat exchanger tubes having enlarged hexed ends l2 suitably stacked together as indicated. The enlarged ends are suitably bonded together by fusible bonding material forming built-up headers 30 as hereinafter described more in detail. The side plates |3 which may be fiat as indicated, or suitably corrugated to fit the tubes, are also bonded to the core It! by the fusible bonding material. Also bonded to the core and to the side plates |3 nected inlet pipe l6 and outlet pipe H, as will be understood by those skilled in the art.

It will be understood that one fluid as, for example, water or other cooling liquid in the case of liquid cooled airplane engines, is introduced into the conduit I6, this liquid flowing around the outsides of the bodies of the tubes l and leaving the heat exchanger by way of conduit H, the flow being indicated by the arrows. The other cooling fluid, which may be air, passes through the insides of the tubes ll, longitudinally thereof, in a direction perpendicular to the plane of the drawing.

It will be seen from Fig. 1 that the core I0 is divided into two areas, an outer area indicated by I8 which may be called the coreshell or frame, this area constituting about four rows of tubes around the entire margin of the heat exchanger; and an inner area indicated by I9 which may be called the core interior, this comprising the re- The hexed ends l2 of the outer area l8 are provided with hexed heat absorbing bushings 2| for a purpose hereinafter disclosed more in detail. The bushings 2| and hexed ends I2 of the area I8, are bonded to each other and to. the adjacent side plates I3 and ducts l4 by hard solder indicated by 28 in Fig. 4 and a superimposed layer of soft solder indicated by 29. The hexed ends of the tubes forming the core interior l9 are bonded together only by soft solder indicated by 29. It will be notedthat the tubes of the core interior l9 do not have any heat absorbing bushings 2|. It will be understood that the heat absorbing bushings 2| in some cases may also be omitted from the tubes making up the core shell lB.-.

The following is given as one example of the method of assembling the present heat ex-.

changer: referring now to Figs. 2 and 3 an outer fixed frame 24 is provided and also an irmer-expansible frame 25 having expandable turn buckles 26. The rows of tubes II to form the core shell H! are stacked between the frames 24 and 25, as indicated in Fig. 2, the frames being arranged to accommodate the desired number of rows of tubes for the core shell or frame It. It will be noted that the frames 24 and 25 fit against the tube bodies 20-, leaving the hexed ends l2 free for the are duct members 4 and I5 to which are conof the hard solder. In case bushings are used the hexed bushings 2 I will be inserted in the tubes making up the core shell I 8 and the hand soldering operation will begin. The silver solder 28 is applied by acetylene blow torch from a wire or rod of silver solder, each joint between each tube and bushing being separately soldered, suitable flux being used. The copper tubes, being extremely thin for lightness and for good heat transfer, would be burned or at least annealed by the high temperatures necessary to melt the hard solder if some heat absorbing means were not provided as, for example, the bushings 2| shown in the drawings.

After both ends of the tubes are hard soldered, the frames 24 and 25 may be removed and the side plates l3 and duct members l4 and I5 may be hard soldered to the core shell l8. In cases where the fiux leaves a residue around the outsides of the tube bodies this will be blown or washed out before adding the core interior IS.

The core interior l9 may now be built up, the necessary rows of nested tubes being placed in position within the core shell or frame I 8, these additional rows being held in position by friction or in any other way well known in the art. The tubes forming the core interior l9. do not have bushings but are otherwise identical with the tubes forming the shell l8. The entire assembled and completed coreis then partially dicated by 29 in Fig. 4 adhering directly to the interior tube ends and to the'hard solder 28 connecting the marginal tubes and the side plates 3 and duct members M as indicated.

In some cases, in order to improve the bonding connection between the tubes, the extreme ends thereof may be bent inwardly as indicated by 33 in Fig. 6, the other reference characters indicating the same parts as-in the other figures.

' This inward bending may be applied either to those tubes'having bushings and to those tubes without bushings to provide increased area of contact between the several bondingmaterials and the tubes.

It should be noted that the indications of solder 28, 29 in Figs. 4 and 6 are largely diagrammatic, no attempt being'made to show'exactly how far the solder runs down into or between the tubes.

Although the radiator according to the invention may vary widely in its.various dimensions, the following is given as an illustrative example of a commercial embodiment used for cooling liquid cooled airplane engines. The individual tubes have an overall. length of 7% inches, the, axial length of the hexes on each end being inch each. The outside diameter of the circular part of the tube is .210 inch and the wall thickness is .006 inch. The tube is of seamless oxygen free copper. The outside dimension from one flat hex surface to the opposite fiat hex surface is .240 inch. The heat exchanger has 65 rows of tubes with 75 tubesin a row, making a total of approximately 4875 tubes. Four rows of tubes on all sides are silver soldered. Such a core-will have a dimension of approximately 8 inches in length (longitudinally of thetubes), a width of may be used, class 4 has proven to be particularly well adapted for this use in practice. Class 4 silver solder has approximately the following composition: 50% silver, copper, 16% zinc, 18% cadmium. It has a melting point of from 1150 to 1170 F. It will be seen that the melting annexed claims, it will be understood that various omissions, substitutions andchanges may be made by those skilled in the art without departing from the spirit of the invention.

. What'I claim is:

1. In a heat exchanger of the cartridge type, a core having its main heat transfer portion made up exclusively of a plurality of similar tubes having enlarged ends spacing the body point of this silver solder is substantially below the melting point. of copper, which is around 2000 F. but that the fusing point of this silver solder runs very close'to the temperatures which may result in serious annealing of the hardened copper tubes. Thus it will be seen why it is neo-.

essary to exercise great care in the silver soldering op ration. The melting point of silver solder is high in contrast to the melting point of ordinary lead-tin solder which ordinarily would run around 500 F.

Thus, a radiator or heat exchanger composite.

core is provided which has substantially as much strength as if the entire core were-hard soldered, while the great labor of hand soldering is greatly reduced. When as many as 5,000 tubes for example may be used in a single radiator, the saving in labor is appreciable. The hard soldered marginal rows provide in effect a shell or frame which is continuous in peripheral extent and which provides an extremely rigid construction for' resisting bending, torsional and vibrational stresses. Thus, the peripheral or marginal tubes which are most effective in resisting these stresses protect the core interior which is relatively ineffective in resisting these stresses and a heat exchanger is obtained which is practically as strong as an all-hand solder type while requiring only a fraction of the work of manufacture; Thus those tubes which are most advantageously situated are bonded with the strongest material.

While certain novel features of the invention have been disclosed and are pointed out in the portions apart, fusible bonding material connecting said enlarged ends to form built-up headers, said headers being divided into a straight sided marginal portion and an interior portion, the bonding material in'said marginal portionbeing hard solder, the bonding material in said interior portion being soft solder, said marginal portion extending continuously around the core and providing a strengthening frame or shell.

2. In a heat exchanger of the-cartridge type,

a core having its main heat transfer portionmade up exclusively of a plurality of similar thinwalled tubes having enlarged ends spacing the body portions apart, relatively thick-walled, heat I absorbing bushings disposed within the enlarged ends of marginal rows of tubes, hard solder con-. necting the enlarged tube ends of said marginal rows, soft solder connecting the enlarged tube ends of the tubes within said marginal rows, said enlarged ends and said solders constituting builtup headers, said marginal rows provided a strengthening frame or shell for the heat exchanger core.

3. In a heat exchanger of the cartridge type,

a core having its main heat transfer portion made up exclusively of a plurality of similar thinwalled copper tubes arranged successively in substantially' parallel rows to define passage for one fluid therethrough, said tubes having enlarged ends spacing the body portions apart to provide space for a passage ofanother fluid aroundthe tubes,, relatively thick-walled, heat-absorbing bushings disposed within the enlarged ends of marginal rows of said tubes, bonding means in cluding silver solder connecting the enlarged ends of the tubes of said. marginal rows, means Y including lead-tin solder connecting the ends of the tubes lying within said marginal rows, said enlarged ends and said bonding means constitutin'g built-up headers, said marginal rows providing a strengthening frame or shell for the heat exchanger core.

- ELHLIEN BLAIS.

Commonly Known as EmileBlair. 

